4._MO_Theory_-_Filled_in

Molecular Orbital (MO) Theory

A bonding model based on wave theory that describes delocalized bonding regions in space about atoms.

Atomic Orbital (AO)

Regions in space around an atom containing a certain energy and probability of electron density.

Bonding Orbital

Formed by constructive interference of contributing AOs, lower in energy and more stable than the contributing AOs.

Anti-Bonding Orbital

Formed by destructive interference of contributing AOs, higher in energy and less stable than the contributing AOs.

Non-Bonding Orbital

Orbitals with minimal mixing between AOs of different atoms, do not contribute to bonding.

Bond Order (BO)

The difference between the number of bonding and anti-bonding electrons divided by two.

HOMO

Highest Occupied Molecular Orbital, containing the highest energy electrons in a molecule.

LUMO

Lowest Unoccupied Molecular Orbital, the lowest energy orbital that is not filled with electrons.

Linear Combination of Atomic Orbitals (LCAO)

A method for forming molecular orbitals by combining atomic orbitals.

Requirements for MO Formation

Atomic orbitals must have similar energies, the same symmetry, and be in close proximity for effective overlap.

Overlap

The interaction of atomic orbitals to form molecular orbitals, which can be bonding or anti-bonding.

Symmetry Operation

A transformation that leads to an equivalent or symmetric configuration of a molecule.

Gerade (g)

Symmetric with respect to an inversion center in molecular orbitals.

Ungerade (u)

Anti-symmetric with respect to an inversion center in molecular orbitals.

Orbital Mixing

The combination of atomic orbitals from different atoms to form molecular orbitals.

Heteronuclear Diatomics

Molecules composed of two different elements, requiring consideration of variations in atomic orbital energies.

Diatomic Molecule

A molecule composed of two atoms, which can be homonuclear (same element) or heteronuclear (different elements).

Paramagnetic

A property of a substance that has unpaired electrons and is attracted to a magnetic field.

Triplet State

A state where two electrons are unpaired, resulting in three possible spin orientations.

Singlet State

A state where all electrons are paired, resulting in a single spin orientation.

s-p Mixing

The interaction of s and p orbitals which can affect the energy levels and characteristics of molecular orbitals.

MO Energy Diagram

A graphical representation showing the relative energies of molecular orbitals and the placement of electrons within these orbitals.

Electronegativity

The tendency of an atom to attract electrons towards itself when forming a chemical bond.

Ionic Character

The degree to which a bond exhibits ionic properties, influenced by electronegativity differences.

Coulombic Bonding

Bonding resulting from electrostatic interactions between charged particles.

Computational Chemistry

A branch of chemistry that uses computer simulations to solve problems about molecular structure and properties.